Katie, 27, attended an event alone on June 13 at Montauk, N.Y. Yacht Club. This is the third marriage for Billy.

Divorce papers have not been filed yet. But are expected to be filed shortly.

UPDATE: The couple’s rep has now issued a statement confirming RadarOnline.com’s earlier exclusive. “After nearly five years of marriage Billy Joel & Katie Lee Joel have decided to separate. This decision is a result of much thoughtful consideration. Billy & Katie remain caring friends with admiration and respect for each other.”